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Generator Runs but No Power | What are the Reasons? How to Fix it?

Storms, blizzards, hurricanes, and other extreme weather conditions are unavoidable, every now and then. The damage caused by these events both in terms of lives, property, and infrastructure is huge. Speaking of infrastructure, it becomes very difficult to supply the electricity in such situations. Hence, many Americans are investing in a backup generator to power all the essential things. If everything works smoothly, then you can simply fuel the generator, turn it on, and start using the electricity. But like all electrical and mechanical devices, even generators are susceptible to problems. One such problem is the generator runs but no power output from it.

In this guide, let us understand the popular reasons why a generator that runs and burns fuel doesn’t produce any power. We will also see how to fix the issue.


Even though the world is moving towards renewable energy, there are some situations where traditional sources of power are the only way to produce electricity. Imagine you are facing a severe snowstorm in years.

It is dark and full of snow outside. Even if you have a solar power solution, chances are it doesn’t produce any electricity due to the lack of sunlight. If the power goes out for days, then you can’t rely on solar and batteries to act as a backup.

This is where gas-powered portable generators become extremely useful. When the grid fails and there is no other way to power your electrical and electronic appliances, backup generators come in very handy.

You can invest in a portable generator, which as the name suggests, is easy to transport from one place to other. The advantage of a portable generator is you don’t have to hardwire it to your existing electrical system.

Just use good quality extension cords and power the appliances off of it. In case you are looking for a more permanent setup, then you can opt for hardwiring the generator.

Speaking of permanent setup, a standby generator is a slightly bigger generator that is usually placed or fixed in one position. Also, the power output of these models is significantly high. So, for regular residential, camping, RV, workshop, or construction site applications, a decent portable generator is more than sufficient.

Generator Runs but No Power

A generator, be it portable or standby, is an electromechanical device. Internally, it has a fuel-powered combustion engine, an alternator, and some additional circuits and components. While gasoline is the main choice of fuel for small and medium portable generators, diesel fuel is the preferred choice for large commercial-grade generators.

Apart from these two, the usage of alternative fuels such as propane and natural gas is also very common.

No matter what fuel you use, the generator is useful only if it produces electricity. If you operate the generator very frequently in situations such as camping, RVs, and worksites, you will not encounter many problems with the generator.

But if you occasionally run the generator in your house only when there is a blackout or power outage, then chances are your generator will cause you some headache.

One common problem with portable generators is it runs, and makes noise, but don’t produce any electric power. If you are unfamiliar with the working and operation of generators, this might worry you and you will start to panic a little bit.

Every generator owner will face a similar problem at least once where the generator runs but no power output from it. The situation is really frustrating as you need electricity from the generator to power some essential electrical devices (there might be even some medical appliances) but it is not producing electricity.

Common Reasons Why Generator Doesn’t Produce Power

If you ever find yourself in such a situation, then you don’t have to worry and call for professional help immediately. First, you have to diagnose the problem and then look for ways to fix it.

Before you do that, the important step is to first understand the reasons why your generator is running and yet not producing power. So, let us take a look at some common and popular reasons why your generator won’t produce electricity.

Poor Electrical Connections

Let us start with something simple. If you are in a situation where your generator run but has no power output, then don’t presume that there is a huge problem with the generator or that something is severely damaged.

The reason you won’t get any power from the generator despite it running, burning fuel, and making noise could be as simple as improper connections. This is especially true if you haven’t taken out the generator in a while or if you left the generator in the garage or shed where dust and debris are blocking the ports.

Tripped or Damaged Circuit Breaker

Circuit Breakers are important safety devices be it in the residential electrical system or portable generators. The purpose of circuit breakers is, well, to break the circuit in the event of overcurrent.

If the circuit breaker detects a current in the circuit over a certain limit (usually the rating of the circuit breaker), it will trip and disconnect the supply to the circuit.

There are two types of circuit breakers in modern generators. They are regular circuit breakers and GFCI Breakers. While regular breakers trip only in the event of overcurrent, GFCI Breakers trip upon detecting a ground fault (in addition to tripping on overcurrent conditions as well).

One of the simple reasons why a circuit breaker trips are if you overload the circuit with a lot of devices and appliances. If you power several devices in the circuit at once, there is a good chance that it overloads the circuit and the breaker trips.

In the case of GFCI, if the breaker detects a ground fault (a situation where the current leaving the hot wire at the outlet and the current returning through the neutral wire isn’t the same), then it will trip immediately. In this way, it can save you from electric shocks.

Regardless of the type of breaker, if it is in a tripped state for any reason, then you won’t get any output at the outlets of the generator.

Another issue with circuit breakers (both regular as well as GFCI) is if there is any damage or problem with the breaker itself, then also the circuit won’t get electricity.

Problem with Outlets

Portable Generators have several outlets to plug different appliances or extension cords into the generator and access electricity. As outlets are the main point of access to the generator’s power, if there is a problem with them, then you won’t have any power at them.

Even though outlets are one of the simplest parts of a generator, there is a chance that the outlet has gone bad (contacts became bad, problem with the wiring, or the outlets are just damaged).

In this case, the generator runs normally but you cannot access its power at the outlets.

Worn-out Brushes

While the previous two reasons are typically on the “outer” part of the generator, we are entering into the problems due to some of the internal parts and components. The first thing to check is the carbon brushes in the alternator.

To be specific, we have to check if the brushes are significantly worn-out. Carbon brushes are one of the most stressed-out components in a generator as they make continuous contact with the rotor and the friction causes them to wear down over time.

Of course, this check is valid only if your generator, or alternator to be precise, uses brushes. Because some modern generators are going the brushless way for the design of the alternator. They might be expensive but you don’t have to worry about brushes in these models.

If there is any damage to the brushes (they wore out due to friction, there are any cracks, or they are completely destroyed), then the alternator cannot output electricity.

Defective AVR

As we are in the vicinity of the alternator, you can check the AVR or Automatic Voltage Regulator module in the alternator. AVR is an important component in modern generators as they help maintain the output voltage at a consistent level.

If the AVR Module is damaged, then you won’t get any output voltage or in some cases, the output voltage will be very low.

Bad Capacitor

In expensive brushless-type generators, you won’t find carbon brushes as the alternator they use could be of brushless type. If this is the case, then the generator might not have an AVR to control the voltage but rather a big capacitor.

The position of the capacitor is similar to where you will find the AVR in the brushed alternator. But unlike AVRs, capacitors hold energy even after we turn off the generator.

So, if you are trying to test its capacitance or voltage with the help of capacitance meters or multimeters, proceed with extreme caution. Don’t touch the terminals of the capacitor with bare hands (particularly, don’t put a finger across both terminals).

This could zap you so hard, give you a severe electric shock, or even burn the skin.

Coming back to a faulty capacitor, if the alternator is working fine (we will see more about this in the next point) but if there is a problem with the capacitor, then you won’t get any power from the generator’s output.

Alternator Lost Residual Magnetism

We have saved the important and perhaps the most common reason for a generator not producing power for the last. While all the reasons we mentioned till now are small and easily fixable, the next reason is somewhat complicated to explain.

If you are familiar with motors and alternators, then understanding this reason becomes very simple. Generators or alternator in the generator produces electricity when a coil in them are subjected to a rotating magnetic field.

Now comes the interesting part. If you open the alternator, you will notice that it doesn’t have any magnets. Alternators use electromagnets instead of actual magnets, where a piece of a coil, a metal core, and a current turn into an electromagnet.

When you turn off the generator, the alternator actually holds this magnetic field so that the next time you start the generator, it uses this magnetic field to give the alternator a “kick-start” until the rest of the components come into action. We call this magnetic field Residual Magnetism.

If you left the generator idle for a long time or if you turned off the generator with a load still connected to it, there is a good chance that the alternator loses its residual magnetism.

If this is the case, then the next time you start the generator, the engine powers up normally but the alternator cannot produce electricity as there is no rotating magnetic field.

How to Fix Generator Runs but No Power Issue?

Now that we have seen different reasons why your generator isn’t producing power, let us see how to fix them one by one.

Before proceeding, we would like to remind you that working with generators can be tricky. Take all the safety measures while opening or diagnosing the issues. That said, let us see how to fix a generator that runs but produces no power output.

Circuit Breakers and Outlets

As usual, let us start with something simple. First, make sure that all the connections are proper. If there is any dust or debris, or if something is blocking the ports of the generator, go ahead and clean it.

Check all the outlets and look for burn marks, physical damage, loose wiring, or completely damaged outlets. Replacing outlets is one of the easiest things.

If the circuit breaker is tripped, reset it. GFCI breakers have a manual test button. If you pressed this button and forgot to reset the GFCI, then simply reset it to see if you are getting power.

Check if you are overloading the breaker. There could be a faulty device or appliance on that circuit or you have connected several power-hungry devices. If the breaker keeps tripping, then this is where you need to concentrate.

But if either the regular or GFCI breaker has gone bad, then you have to replace it with a new one. Don’t bypass the breaker in any case. They protect you from shocks and prevent fires. If you have a damaged breaker, do replace it with a functional one.


As we mentioned earlier, carbon brushes are one of the easily stressed-out parts of an alternator. Look at the state of the brushes. If they are completely worn out or damaged, replace them with new ones. They are very inexpensive.

Due to the constant friction, there is also a chance that brushes are displaced. Even though this is rare, you can check and see if the brushes are in their determined position or not.

AVR and Capacitor

In the case of alternators with brushes, you will have an AVR keeping a check on the output voltage. You can check the voltage of the AVR with the help of a multimeter. If the voltage on each phase of the alternator is around 75V, then the AVR has gone kaput. It is time to replace it.

Similarly, if you have a fancy generator that uses capacitors instead of AVR, then first check its capacitance and see if the meter reading is close to the actual rating of the capacitor (this will usually be printed on the side of the capacitor).

While you are there, you can also check the voltage across the terminals of the capacitor. If the voltage reading is very low (between 5 to 10V), then the alternator might be fine but the capacitor is faulty. You have to replace the capacitor.

Flashing the Alternator

In the previous fix, we measured the voltage across the phases of the alternator and determined that if the voltage is around 75 to 80V, then the alternator is fine. But what if the voltage across the phases is very low, somewhere around 5V or even less?

This usually means the alternator lost its residual magnetism. Before fixing this, let us quickly see how can we prevent the loss of residual magnetism.

Before turning off the generator, switch off all the loads (devices, appliances, lighting, tools, etc.), especially motor-based ones and disconnect them from the outlet of the generator. This way, the loads don’t pull the last chunk of energy from the alternator.

If you keep your generator idle or unused for a long period, it might drain the residual magnetism and doesn’t produce electricity the next time. So, don’t let the generator parked for a long time. Use it from time to time. Just turn it on, connect a small load (don’t run the generator without load), run it for 5 to 10 minutes, disconnect the load, and turn off the generator.

Now that we have seen how to prevent loss of residual magnetism, let us understand what to do if the damage is already done i.e. if the generator is running, burning fuel, but the alternator isn’t producing any power. As this is usually the case of loss of residual magnetism, you somehow have to regain this magnetism. Here are a couple of ways you can do this.

Using Battery

For the first method, you need a 12V car battery or a jump starter pack. Connect the negative terminal of the battery (or the jump starter) to any grounding point of the generator. Now, connect a load (a slightly powerful incandescent lamp would do fine) and start the generator.

Once the generator is up and running, connect the positive terminal of the battery (or jumper pack) to the red-colored carbon brush in the alternator. Continue this for 5 to 8 seconds and then you can disconnect the battery.

You can then re-position the brushes. An important price of caution. Disconnect the AVR while you are doing this and be careful while you are around the AVR.

Using Drill

If you don’t have a spare battery (or a jumper pack), then how to regain the residual magnetism? Don’t worry. If you have a corded electric drill, then there is a neat little trick for you.

Plug the electric drill into one of the outlets of the generator. Don’t connect any drill bits to the chuck of the drill and make sure that the rotation of the drill is set to forward. Turn on the generator, pull the trigger and now manually rotate the chuck of the drill in a counterclockwise direction. Don’t hold the chuck too tight and you have to twist it about 3 to 5 times. This will “flash or re-magnetize” the alternator and kick-start it. As you pressed the trigger, it will start rotating the drill and you are good to go.

If you ever played with motors, you will understand how this works. When we connect the motor to a source of power, it starts spinning. But if you manually rotate the shaft of the motor, then it produces electricity. We are using this electricity from the electric drill to produce a magnetic field in the alternator.


Portable Generators are very useful in certain situations. Natural disasters such as storms, floods, etc. might interfere with the supply of electricity and you have to rely on alternative sources of power such as generators.

You took the generator from its storage, filled up the fuel, and started it. But even though it is running, you will notice that it isn’t producing any power or electricity. However frustrating this is, the problem is quite common with generators.

In this guide, we saw the basic reasons why your generator runs but no power at its output. We also looked at some simple ways to fix the issue.

We hope that this guide could help you fix your generator that isn’t producing any power. If you feel we missed something or want us to add anything, do let us know in the comments section. It will not only help us but also other readers as well.

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